Dreaming about a spare motor

AKJohne

Petty Officer 1st Class
Joined
Mar 26, 2017
Messages
220
I have a 24' glass boat with a 1997 5.7 LX, Alpha 1 G2. The boat is heavy but it runs good and we can typically cruise around 22 to 25 knots at 3100-3300 RPM. 2.1 MPG. 4600 WOT.

Motor has 300+ hours and runs fine, however it is a rebuilt motor and I just dont really know what to expect for a usable life out of this motor, nor what and or how it was rebuilt.

With that being said I have been thinking about having a spare engine, all my boating is in Alaska and the season is relatively short, a breakdown requiring a motor replacement would likely put me out of commission for the season, if I had a spare I could swap it out in a long weekend. And not be under the gun to come up with a engine. Maybe sounds extravagant, but at 65 I dont want to sit out a season.

Current motor has mech fuel pump and 4bbl, I would prefer to stick with that setup, it is also pre-vortex.

There are plenty of choices for long blocks, either new or rebuilt in the states, however shipping to AK can add up.One thing about GM small-blocks is they are plentiful as are the parts. I was in a local machine shop and he figured he could build a roller cam motor for about 3K.

The big question is, what would you guys recommend? This is a heavy 6-7K cabin style boat that we use for fishing and overnight primarily in Prince William Sound. I know I am somewhat limited by the A1 rating of max 300HP, however I do not need to do full throttle takeoffs, I wont be wave jumping and WOT is reserved for propping and emergency. I think I would be ok w/ 330/350 HP... IMHO.... Maybe the bigger concern perhaps is torque. I would like to see max torque at the RPM range we typically cruise at or slightly lower if possible.

If given these parameters what would you guys build? I am planning on using a Vortex block, with new intake, So.... type of cam? Pistons? Roller rockers? Rocker ratio? assuming a stock rotating assembly and rods would be OK for this.....

THANKS.....!
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
I think you’d be just as well served by just doing frequent oil changes, and preventative maintenance on consumable parts like exhaust manifolds and risers. No reason why these tried and tested engines wouldn’t go on for ever, or at least degrade progressively and predictably, with routine and preventative maintenance.

Good chance you could go down the route of spending thousands on a spare engine and never use it.

a compression check will tell you the health of your motor then go from there. Most common cause of failure on these is things like neglect and corrosion of manifolds.
 

AKJohne

Petty Officer 1st Class
Joined
Mar 26, 2017
Messages
220
I think you’d be just as well served by just doing frequent oil changes, and preventative maintenance on consumable parts like exhaust manifolds and risers. No reason why these tried and tested engines wouldn’t go on for ever, or at least degrade progressively and predictably, with routine and preventative maintenance.

Good chance you could go down the route of spending thousands on a spare engine and never use it.

a compression check will tell you the health of your motor then go from there. Most common cause of failure on these is things like neglect and corrosion of manifolds.

Thanks, I have stayed on top of the maintenance, done both compression and leak down test. Dealt with mannies last year...Its solid as we speak, however I doubt it will go on forever... what is the practical life of a well cared for 350...? 1000 hours? More?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Barring catastrophic failures (water ingress etc) 2500 hours/25 years is not unusual, even on a rebuild if it was done acceptably.

I have a friend with a 28' Bertram, twin 1984 SBC engines. The thing killing those engines is corrosion. Still plenty of Alpha Ones (sometimes called 'Gen one') still going, and when you think that the Gen II arrived 29 years ago...

Chris.....
 
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QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Thanks, I have stayed on top of the maintenance, done both compression and leak down test. Dealt with mannies last year...Its solid as we speak, however I doubt it will go on forever... what is the practical life of a well cared for 350...? 1000 hours? More?

It’s subjective I suppose. What kills them is not using them and leaving them exposed to corrosion over winter.
being European, 260hp from an engine that size is far from being stressed. Well cared for, it’s more likely the electrics and other things will fail round about the engine. Salt and fresh water use have an influence on such things. These GM engines aren’t in my opinion, the most popular power plants ever seen in a boat for no good reason. Put simply, they are tried and tested over the last 4 decades. Not many power plants can boast that.
 

AKJohne

Petty Officer 1st Class
Joined
Mar 26, 2017
Messages
220
Good info, the boat sits inside a heated shop over the winter, might not be able to do that every-winter... I can as long as I am still working and have a shop anyway. It gets plenty of love in terms of maintenance, folks call me a good boy scout... haha....
Guess I dont like being broke down in remote spots or relying on others to save my azz....

I was thinking 1000 hours might be it, guess I can save my money. Likely need a lower unit first..........!
 
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